Laundry detergent granules comprise one or more surfactants (usually of the anionic type) and one or more detergency builders (typically phosphates, carbonates, zeolites, etc.) Detergent granules are typically made by preparing a paste of the detergent ingredients, and spray drying the paste to form granules. Such products also can be made by agglomerating a mixture of the surfactant and builder in a mixer. In an agglomeration process, the anionic surfactant in its neutralized form can be used or it can be introduced into the agglomeration process in its acid form and be neutralized in situ by alkaline materials (e.g. sodium carbonate). Optional detergent materials such as brighteners, soil release agents, etc. can be agglomerated along with the surfactant and builder or can be mixed with the agglomerates after they are formed. Generally, agglomeration provides the ability to produce higher density detergent products than those which are produced by spray drying.
A frequent problem with detergent agglomerates, particularly those having a surfactant level of 20% or more, is a tendency to be somewhat sticky (i.e., poor free flow). To help alleviate this problem, flow aids such as clay, talc, zeolites or silica are typically used.
Representative examples of prior patents relating to agglomeration processes for the production of detergent granules are: U.S. Pat. No. 5,133,924 (Appel); U.S. Pat. No. 5,164,108 (Appel); U.S. Pat. No. 5,160,657 (Bartolloti); Brit. Pat. 1,517,713 Unilever); Euro. Appln. 451,894 (Curtis); U.S. Pat. No. 5,108,646 (Beerse et al.); Euro. Pat. Appln. 351,937 (Hollingsworth et al ); and U.S. Pat. No. 5,205,958.
The object of the present invention is to provide a process for producing detergent agglomerates having high surfactant levels and improved free flow characteristics.